Census and hospital discharge data from Sweden and Denmark and U.S. Veterans hospitals, linked for follow-up to cancer, mortality, and population registries where available, were used to assess cancer risk among individuals with specific medical and occupational exposures. Patients with two types of porphyria (porphyria cutanea tarda and acute intermittent porphyria) in both Sweden and Denmark had an increased incidence of liver cancer and lung cancer, as well as increased mortality from non-malignant respiratory conditions. Diabetic patients in Sweden were found to be at increased risk of renal cell carcinoma. Mortality among diabetics was elevated for all major causes of death, particularly circulatory, respiratory, digestive, genito-urinary, and malignancies. The youngest diabetics had the greatest increased mortality from all causes. Obese patients were at increased risk of cancers of the digtestive tract, urinary tract, female reproductive organs and connective tissue. Swedish patients with hemochromatosis had a cumulative risk of hepatic cancer of 10% after about nine years. Swedish gallstone patients with cholecystectomy had an increased risk of cancers of the pancreas and ampulla of Vater, as compared to gallstone patients without cholecystectomy who had an increased risk of liver and gallbladder cancers. Celiac patients had an increased risk of lymphoma and cancers of the upper digestive tract. In Danish and U.S. Veterans hospital data, we investigated the link between inflammatory bowel diseases (ulcerative colitis and Crohns disease), appendectomy and cancer. We found no evidence of a reduced risk of ulcerative colitis subsequent to appendectomy in either Danish patients or U.S. veterans. In contrast to patients with ulcerative colitis, Crohns disease patients were at increased risk of cancers of the small intestine, but not colorectal cancers. Danish women with molar pregnancy were not found to be at increased risk of any cancer other than gestational choriocarcinoma. Danish women hospitalized with gonorrhea were at increased risk of cervical pre-neoplasia, but not invasive cervical cancer or any other cancers. Analyses of Swedish census data have found no general healthy worker effect for cancer incidence among employed Swedish women. An increased risk of endometrial cancer, but not breast cancer, was found for women with sedentary occupations. Swedish census data also revealed an increased risk of lymphoma associated with residence in Southern versus Northern Sweden, however outdoor occupations were not associated with increased risk. Swedish men and women employed in occupations exposed to diesel engine emissions showed increased risks of respiratory and digestive cancers, and also cervical cancer among women. Butchers and other meat workers were also at increased risk of respiratory and digestive cancers. - occupation, medical conditions, risk factors, hospital patients, medical procedures, - Human Subjects & Human Subjects: Interview, Questionaires, or Surveys Only